Engine oil system and acceleration responsive control means therefor



O t- 11. 1955 w. D. TEAGUE, JR. ETAL 2,720,282

ENGINE AND ACCELERATION 0 SYSTEM RESPONS CONTROL MEANS THEREFOR FiledMarch 24, 1951 2 Sheets-Sheet l FIG.|

422 i EH24 E %1 p 2' A 2+ INVENTORS HOWARD H. LAUC/(S WALTER 0. 75/1605JR.

1955 w. n. TEAGUE, JR.. ET AL 2,720,282

ENGINE OIL SYSTEM AND ACCELERATION RESPONSIVE CONTROL MEANS THEREFOR 2Sheets-Sheet 2 Filed March 24, 1951 INVENTORS WALTER D. TEAGUE JP.

LAUCKS HOW/4RD H.

grrowzy 01L SYSTEM AND ACCELERATION RESPONSIVE CONTROL MEANS THEREFORWalter D. Teague, In, Alpine, and Howard H. Lau cks, xSparta, N. J.,iassignors ito Bendix Aviation COI'PGIQHOI],

Teterhorlo, N..J., a corporation of Delaware Applicafiun Mar 24,195 ,Ssia 11 394 6 Claims. (Cl. '1846) This invention relates generally {toengine oil systems and more particularly to improvements in an engineoil system embodying a protective device for automatically bypassing theoil cooler of the system such as disclosed and claimed in copendingapplication Serial No. 130,157 filed November 30, 1949 by Walter D.Teague, Jr. and assigned to Bendix Aviation Corporation.

'YIihe present invention contemplates the provision of accelerationresponsive means for controlling the automatic operation of theprotective device set forth in the aforenoted application Serial No. 1 30,;1 57.

The protective device disclosed in application Serial No. =1'30,157comprises a valve adapted for inclusion in an engine oil system of an"aircraft and which embodies means -"for .sensingthe -flow of oil to andfrom the engine oil cooler. In the 'eventthe return flow issubstantially less than -the flow tothe cooler, the valve operates toby-pass the cooler. i i However, certain movements of an aircraft suchas a rapid climb, a recovery from a dive or asudden upward -verticalmovement ;in response to a thermal, produce an acceleration which is{termed a positive -G acceleration; while other movements of an aircraftsuch as asudden-dive or vertical downward movement due to a down draughtproduce what is known as a negative G acceleration. It has been foundthat where these negative or positive G accelerations are of arelatively high order, a slugiof airmay 'become entrapped "in the oillines orconduits of the oil system. Such G accelerational forces -maycause displacement of the oil at theintake of theengine'scavenger pumpso that the pump may draw -a portion or slug of air into the oil conduitleading to the oil cooler. This air slug when passing through theaforementioned valve causes the automatic hy-pass operation thereofsince its momentary eifectin passing through thevalve, *iS the sameaswould be=produced by-a leak in the oil cooler.

kTO overcomethis undesirable operation of the valve the instantinvention-proposes means whereby the automatic operation of the valvedue to such an air slug may bemomentaril-y delayed -t ojthe end that theair slug-maypass through-t he oil systemWithout causing the automaticoperation ;of the valve and the subsequent bypassing ofthe oil cooler.

A-furtherobject of the present inventionisthe prov-ision. ofGacceleration responsive means for controllingrthe actuationof-anelectronic-timing device.

.iAnstillfnrtherrobject of ttheipresent inventionsis the limvisionofmeans .1 adapted and arranged to control a the actuation of anelectrically operatedscontrol device in rsspqas .t 56 isaqq l at on t opr ds r as .tudes.

tT enr se t .i Y nt als o template m an wher ay-s ag sta i Q L an e ldeviq ca ied. b a e craftmanbemsm ntmi da aye i reasonable-a ch n t hzag el rat o l of lik ai cra .Th i-fo eg n an rqth i bject a xadvan aswil appea m r r fu ly here naft .1: r m t musideta n o the detaileddescription which follows, taken together with the accompanying drawingwherein one embodiment of the invention is illustrated by way ofexample. It is to be expressly understood, however, that the drawing isfor the purpose of illustration only and not to be construed as definingthe limits of the invention.

Referring to the drawing wherein like reference characters designatelike parts,

Fig. l is a diagrammatic illustration showing in phantom a side View ofan engine nacelle and the instant invention associated with the engineoil system of an aircraft;

Fig. 2 is a section through line 2-2 of Fig. 3;

Fig. 3 is a section through line 3 -Zi of Fig. 2;

Fig. 4 is a section through line 4-4 of Fig. 2; and

Fig. 5 is a schematic illustration disclosing the bypass .valve system.

Referring now to the drawing and more particularly to Fig. l, thereference character A designates an aircraft engine nacelle in which ismounted an engine oil system] The engine oil system comprises a sump 10connected through a conduit 12 to an engine 14, and a pump 16operatively positioned in the conduit 12 draws oil from the sump 10 anddelivers it to the engine 14. Oil is pumped from the engine 14 by ascavenger pump of conventional type embodied therein through conduit 18from whence it passes through the bypass valve -20, conduit 22, oilcooler 24, conduit 26, by-pass valve 20 and conduit 28 to the sump 10.Thus, a normal oil circuit, including cooling means for the oilisprovided for the engine 14.

The by-pass valve 20.is of a=type described and claimed in the copendingapplication Serial No. 130,157 filed November 30, .1949, by Walter D.Teague, Jr. and includes means responsive to the flow of oil to and fromthe oil cooler 24 so that should a serious leak develop in conduit 22,the oil cooler 24 or conduit 26, the bypass'valve 20 automaticallyoperatesto by-pass the oil through the valve 20 to the Iconduit 28 .andthence to thesump 10. Thus, an emergency fluid or oil circuit fromtheengine 14 to thesump .10 is provided in which the coolingmeans 24 isbyepassed.

In filling the oil system, the initial flow of oil there throughproduces a conditiontherein that is similar to the condition caused byaleak in the cooling system so that the oil flow responsive controlmeans, .hereinbefnr described, causes operation of the valve 29 toestablish the :by-pass circuit hereinbefore set forth. To provide meanswhereby the oil system may be completely filled. a manually operatedswitch 30 is suitably connected through an electrical circuit 32 toenergize a solenoid operated valve 34. The solenoid valve 34-when s6energized isradaptedrtoprevent.the automatic operation of the valve-:20to theend that anormalfiow of oil through the entire oil system ismaintained during the filling operation. In short, the solenoid valve 34serves to per mit a normal flow of oil throughthe system including theoil cooler 24under conditions which would usually result in theemergencyoperation of bypass valve -20 toby-passthe oil cooler 24.

The specific structureof the automaticby-pass means 20 above setforth,forms nop'art of the instant invention and reference ismade to theaforenoted copending application Serial No. 130,157 for a detaileddescription of the construction and operation of the various elementsthereof.

As hereinbefore ,set forth, certain movements of .an aircraft such asextreme ,upward or downward movementsthereof may produce slugs of air inthe oilsytem tending to cause, premature operation of the by-passvalve20 10, establish thebyrpass circuit. -;The,present inventioncontemplates lutilizing the control exercised .bysthe solenoid valve 34over the by-pass valve 20 to produce under such extreme flightconditions of the aircraft, a delay in the operation of the valve 20 tothe end that the air slug may pass through the oil system withoutcausing the emergency operation of the by-pass valve 20.

To that end, there is provided an acceleration switch 36 responsive tosuch extreme upward and downward movements of the aircraft and anelectronic timing device 38 electrically associated with the solenoidvalve 34 and controlled by the acceleration switch 36. The switch 36 inresponse to positive or negative accelerations of a predeterminedmagnitude caused by the aforenoted extreme movements of the aircraft, ashereinbefore set forth, initiates operation of the electronic'timingdevice 38 so as to effect energization of the solenoid valve 34 for apredetermined period so as to prevent the automatic operation of theby-pass valve 20. Thus by delaying the automatic operation of the bypassvalve 20, in response to the flow of oil to and from the oil cooler, theslug of air caused by such extreme movements of the aircraft may passthrough the oil cooling system without having the by-pass valve 20respond thereto.

The by-pass valve (Fig. 5) includes a pair of axially adjoining chambers145, 147 communicating with each other through an intermediate reducedpassage 149, and further includes a second pair of axially adjoiningchambers 150, 151 communicating with each other through an intermediatereduced passage 152. Adjacent chambers 145 and 150 communicate with eachother through a reduced passage 153. Communication between the lattertwo chambers is normally blocked by the land 154 of a plunger 155.Normal circuit flow is from the engine over line 18, through chambers145, 147, and line 22 to the oil cooler, and from the latter by returnline 26 through valve chambers 150, 151 to the sump line 28. Aconstriction 156 is provided in line 18, from either side of whichconstriction run lateral pressure lines 157, 158. Plunger 155 carries atopposite ends lands 159 and 160, one carried by the plunger in a chamber161, the other carried in a chamber 162. Lateral line 157 connects withchamber 162 to the rear of land 160, and a branch 163 thereof connectswith a chamber 164 in the upper end of a servo valve 165. Lateral line158 connects with a chamber 166 at the opposite end of the servo valveand communicates through the valve opening 167 over line 168 with thechamber 161 to the rear of plunger land 159. A constriction 169 isprovided in oil cooler return line 26, from one side of which a lateral170 extends to a central chamber 171 of the servo valve, and a lateral172 extends to a second central chamber 173 of the servo valve. Chamber171 is partitioned from chamber 173 by a wall 174. The joining shaft 175of an H- shaped plunger 134 is slidable in the wall 174. Chamber 164 isabove one head 176 of the plunger, and chamber 171 is below; chamber 166is below the other head 177 of the plunger, and chamber 173 is above it.

The pressures over the various lines to the rear of the opposite landsof the by-pass valve plunger 155, together with the bias of a spring 178in the chamber 161, hold plunger 155 in its normal position, asindicated. The pressures over the various lines to the servo valve,together with the bias of a spring 179, hold the servo valve 167normally open, whereby pressure fluid flow is maintained over line 168to the spring end of plunger 155.

When the pressures to the servo valve are upset by a leak in the oilcooler circuit or by a slug of air passing through the oil coolercircuit, the servo valve 167 closes and pressure flow to the spring endof plunger 155 is cut off. When this happens, the forces acting onplunger 155 are unbalanced and the plunger is forced leftward to carryspaced lands 154 and 180 to seat in reduced passages 149 and 152,whereby valve fluid flow to and from the oil cooler system is cut off,and the fluid flow is bypassed from the engine line 18 directly throughchambers 148 and 150 to the sump return line 28.

The solenoid valve 34 is used to prevent this by-pass action when a slugof air passes through the oil cooler system. Valve 34 is positioned in aline 181 shunting lateral line 158 with line 168 and is normally closed.When the solenoid valve 34 is energized by the action of switch 36,communication between lines 158 and 168 is opened and is continued bythe timing mechanism 38 for a time suflicient to allow the air slug topass through the oil cooler system.

The specific structure of the electronic timing device 38 per se formsno part of the instant invention and any of the conventional timingdevices well-known in the art may be used or the same may be of a typesuch as disclosed and claimed in the U. S. Patent No. 2,444,- 210granted June 29, 1948, to John W. Lauricella and assigned to BendixAviation Corporation. Operation of the timer 38 is initiated by theclosing of the switch 36 and the timer 38 is arranged to effectenergization of the solenoid valve 34 during its operation for apredetermined interval of time to delay or prevent the automatic op:eration of the by-pass valve 20 for such predetermined interval of time.The predetermined period of time during which the electronic timing unit38 is to energize the solenoid controlling the valve 34 is based ofcourse upon the estimated time required for the slug of air to passthrough the oil system after the acceleration condition producing thesame has ceased. The timing unit 38 is therefore so adjusted as toeffect after operation thereof has been initiated by the accelerationswitch 36, the energization of the solenoid controlling the valve 34 fora period of time sufficient to permit the slug of air to pass throughthe oil system without effecting the automatic operation of the by-passvalve 20.

The acceleration switch 36 per se is described and claimed in co-pendingdivisional application Serial No. 279,262, filed March 29, 1952, in thename of Walter D. Teague, Jr. and Howard H. Laucks.

The acceleration switch 36 shown in detail in Figs. 2, 3 and 4,comprises a housing 40 having an end wall 42 formed integral therewith,and a removable cover plate 44 that is adapted to be mounted on thehousing 40. Suitable fastening means, such as bolts 46, pass through thecover plate 44 and end wall 42 to removably secure the cover plate 44 tothe housing 40. The bolts 46 also serve as means whereby the switch 36may be mounted to'a supporting structure 48. The housing 40 and coverplate 44 may be formed of any suitable dielectric material.

A bracket 50 secured to the housing 40 by a rivet or bolt 52 has alateral arm 54 that extends into the housing 40 and serves to supportelectrical contacts 56 and 58. Since the housing 40 is of dielectricmaterial, the bolt or rivet 52 is utilized as a conductor to connect thecontacts 56, 58 to a terminal bar 59 mounted to the housing 40 by therivet 52. It is to be noted that the contacts are so positioned as to besubstantially equally disposed on each side of the horizontal axisx--x-of the switch 36.

As shown in Fig. 4, the end wall 42 and cover plate are provided withcylindrical recesses 60 and 62 respectively, which serve as journals forthe opposed ends of a transverse shaft 64. The length of the shaft 64being so dimensioned that when the cover plate 44 is secured to thehousing 40 by the bolts 46, the shaft 64 is secured against sidemovement between cover plate 44 and the end wall 42. It is also noted,that the axis zz of the shaft 64 is normal to the horizontal axis x--xof the switch 36 shown in Fig. 2.

As shown in Fig. 2, the shaft 64 affords means whereby a weight orinertia mass 66 is pivotally mounted for rotation about the axis zzwithin the housing 40. The weight 66 may be made of any suitableelectrical conductive material and comprises a body portion 68 havinglateral extensions 70 and 72 adapted to carry adjustable electricalcontacts 74 and 76 respectively, an extension 78 havingaligned studs 80and 82,-and an arcuate arm 84 that is held in spaced relationship withrespect to the body 68 by the extension 78. The arm 84, as shown in Fig.4, is provided with a bore whereby the weight 66 is pivotally mounted onthe shaft 64. As shown in Fig. 4, spacers or washers 88 mounted on shaft64 and interposed between the weight 66 and the inner surfaces of thecover plate 44 and end wall 42 centrally position the weight 66 on theshaft -64 and prevent any side movement thereof on the shaft 64.

As shown in Fig. 2, the center of gravity C. G. of the weight '66 islocated in the body portion 68 thereof, and therefore, is at a pointremoved from the pivot or shaft 64. It is apparent, therefore, that whenthe switch 36 is positioned as shown in Fig. 2, the force of gravity"acting on the weight 66 tends to rotate it in a clockwise directionabout the axis z-z. This rotation of the weight 66 is resisted inpartbya compression spring 90 that is *operatively positioned between acap 92 that engages the stud 80 and a cap 94 that engages a stud 96.adjustably mounted in an extension 98 of the housing 40. The stud 96 isexternally threaded as at 100 to engage internal threads formed in thehousing 40 and its extension 98. A slot 102 in the head of the stud 96affords means whereby the stud 96 maybe moved relative to the "housing40 to thereby adjust the biasing eifect of the spring 90 on the weight66. A nut 104 threaded on the stud 96 serves to secure the stud 96 inits adjusted position. A second compression spring 110 is operativelypositioned between a cap 112 that engages the stud 82 and a cap 114engaged with a stud 116 that is also adjustably mounted in the extension98 of the housing 40. The spring 1'10also serves to resist the clockwiserotation ofthe mass 66 about its shaft64. As shown in Fig. 2 theextension 98 is "internally threaded to engage the external threadsof'the stud 116. A slot 118 in the head of the stud 116 affords meanswherebythe stud 116 may be moved relative to the housing 40 totherebyadjust the force exerted by the spring 110 on the cap 112 and a nut"1'20on the 'stud116 locks the stud 1 16 in its adjusted position. Thecap 112 is provided with lateral flanges 122 that are slidably receivedon slots or recesses 124 and '126 formed in theend wall 42 and coverplate 44, "and these slots are so positioned as to prevent any movementof the cap 112 above the horizontal axis x-x of *the switch36. It isapparent therefore, that any loading of the spring 110 will not effectthe movement of the 5 mass 66 in a counter-clockwise direction above thehorizontal axis xx of the switch 36. However, any rotation of theweight66 that would displace its center of gravity C. G. to a pointbelow thehorizontal axis x--x of the switch 36 is resisted by both thesprings 90 and 1 10.

A flexible cable or wire 130 havingone end thereof connected to the arm84 passes through an opening .in the wall of the housing 40 and isconnected at the other end thereof to a terminalbar 132 secured tothehousing 40 by a' bolt or rivet. Thus, a circuit between terminal bars59 and 132is established through the weight 66 and cable 130 upon theengagement of either the contacts 56 and 74 or 58 and 76. Should itprove advantageous to use a di-electric material for the mass or weight66, suitable electrical leads through the same may be pro vided toconnect the contacts 74 and 76 to the terminal 132.

In order to initially adjust, or set, the switch 36 for response topredetermined negative and positive accelerations, the switch 36 ispositioned so as to have the longitudinal axis xx thereof horizontal.Thus, the switch 36 will be positioned as if it were mounted in anaircraft with the axis x-x of the switch 36 in alignment with the lineof level flight of the aircraft. It is apparent, that when the switch 36is so positioned, the force of gravity acting on the weight 66 will tendto rotate it in a clockwise direction about the shaft 64. The springs 90and 110 are then adjusted so as to pro vide a biasing force against theweight 66 that positions the C. G. thereof substantially on the axis x-xof the switch 36. It is to be noted, that it is the sum of the forcesexerted by the springs and that balances the weight 66 in this position.However, as here'inbefore .set forth, the spring 110 is provided with acap 122 which operates in recesses 124 and 126 to the end that thespring 110 cannot exert any force against the weight 66 when the C. G.thereof is above the. longitudinal axis x-x of the switch 36. Therefore,it is apparent, the spring 90 may be adjusted to exert any desiredbiasing force and the spring 110 contributes only that force required tobalance the weight 66 with the .C. G. thereof on the longitudinal axis xx of the switch 36 the remainder of the force within the spring 110being operative through the flanges 122 on the cap 112 against the'endwall 42 and cover 44. Thus, regardless .of the force within thespring 110 due to its compression between the caps 114 and 112, the onlyforce contributed thereby to the balancing of the weight 66 asaforesaid, is the difference between the force exerted by the spring 90and the total biasing ,force required to position the C. G. of theweight 66 on the longitudinal axis x-x of the switch 36. Due to thisconstruction and arrangement .of parts, the rotation of weight 66 in acounter-clockwise direction on its shaft 64 in response to negative Gaccelerations, i. e., downward movements of the switch 36, is assistedonly by the spring 90. Therefore, .by varying the force contributed bythe spring 90 to the balancing of the mass 66 the sensitiveness of theswitch 36 to negative G accelerations may be varied. The rapidity ofresponse of the switch 36 to negative G accelerations may also becontrolled by adjusting :the distance between the contacts '53 and ,76.

Rotation of weight 66 in a clockwise direction on its shaft 64, inresponse to positive G accelerations, i. e., upward movements of theswitch 36, is controlled 'byboth the springs 90 and 110. As hereinbefore'set forth, the weight 66 is balanced on longitudinal axis xx by thecombined biasing forces exerted by the springs 90 and 110, therefore,any clockwise rotation of the weight 66 in response to positive 'Gaccelerations is resisted by these springs. Moreover, while the spring"110does not-efiect the counter-clockwise rotation of the mass 66 wherethe CG. thereof is on or above the axis x-x, the recesses 124 and 126permit the compression of the spring '110 by'the mass 66 as .it rotatesin a clockwise direction. It is apparent, therefore that by varying theforce within the spring 110 the resistance thereof to compression by theweight .66 during the clockwise rotation thereof in response to positiveG accelerations, may .also be varied to the end thatthe switch 36 may bemade more or less sensitive to positive G accelerations. The rapidity ofthe response. of the switch '36 to positive G accelerations may also 'beadjusted by varying the distance between the contacts 56 and 74.

When the switch 36has been adjustedto respond to a:desired negative andpositive acceleration as herein- :be'fore set forth, it is mounted inthe aircraft so as to have the axis x-x thereof parallel to thelongitudinal axis of the aircraft and the axis z--z parallel to thelateral axis of the aircraft. The switch 36 is electrically associatedwith the timer 38 through leads 136 and 148 which connect the terminals132 and 59 respectively, to the terminals of the timer 38. A powersource 140 for the circuit is inserted in the lead 136.

The electronic timer 38 in turn, is connected through leads 144 and 146to the solenoid valve 34.

Since the axis of rotation z-z of the weight 66 is parallel to thelateral axis of the aircraft and normal to the longitudinal axis of theaircraft it is apparent that linear accelerations or changes in thespeed of flight of the aircraft along the line of flight FF of theaircraft A will not eflect the operation of the switch 36. However, uponan upward vertical movement of the aircraft or recovery of the aircraftfrom a dive effecting a posioil system as a result of the positive Gacceleration of the aircraft, the flow responsive control means of theby-pass valve 20 is prevented from operating the by-pass valve 20 inresponse thereto to the end that the flow of oil through the normalsystem is uninterrupted. In the event a leak has developed in the oilcooler, it will be seen that upon deenergization of the solenoidcontroiling the valve 34 by the timer 38 at the end of the delay period,the valve 20 will operate to establish the by-pass circuit ashereinbefore set forth.

Similarly upon a downward vertical movement of the aircraft effecting anegative G acceleration in excess of the adjusted value of the switch 36the Weight 66 rotates in a counter-clockwise direction about its axis zzcausing contacts 58 and 76 to close to initiate operation of the timer38 for effecting the operation of the solenoid valve 34 hereinbeforedescribed.

It will be apparent from the foregoing that a novel improved engine oilsystem is provided wherein the several objects and advantagescontemplated by the instant invention have been achieved.

Although only one embodiment of the invention has been illustrated anddescribed various changes in the form, relative arrangement andapplication of the various elements may be made without departing fromthe spirit and scope of the invention as will now be understood by thoseskilled in the art.

What is claimed is:

1. In a fluid system adapted for use in an aircraft and including afirst circuit for circulating a fluid through a cooling means, firstvalve means automatically operable in response to a predeterminedcondition of flow through said cooling means to establish a second flowby-passing the cooling means, and second valve means operable to preventthe automatic operation of said first valve means, the combination withsaid second valve means of negative and positive G accelerationresponsive means adapted and arranged to control said second valve meanswhereby the automatic operation of said first valve means is delayed inresponse to changes of predetermined magnitude in the negative orpositive G acceleration of said aircraft.

2. In a fluid system adapted for use in an aircraft the combination ofcircuit means for circulating a fluid through a cooling means, firstvalve means in said circuit means automatically operable in response toa predetermined flow in said cooling means to establish a second flowthrough a portion of said circuit means by-passing means operable toprevent the automatic operation of saidfirst valve means, and meansincluding an electrical timing device and a negative and positive Gacceleration responsive switch electrically associated with saidsecondvalve means for controlling said second valve means to delay theautomatic operation of the first valve means.

3. In a fluid system including a first circuit for circulating a fluidthrough a cooling means, first valve means automatically operable inresponse to a predetermined condition in said first circuit to establisha second circuit by-passing the cooling means, and second valve meansoperable to prevent the operation of said first valve means, thecombination with said second valve means of negative and positive Gacceleration responsive means constructed and arranged to control saidsecond valve means to delay the automatic operation of said first valvemeans as aforesaid.

4. The combination with an aircraft engine oil cooling system of by-passmeans adapted to function and by-pass the cooling system in response topressure drops due to leakage or slugs of air in the oil flow throughthe cooling system, the slugs of air in the cooling system arising frompositive and negative G accelerations of the aircraft, and electricallyoperated means responsive to the positive and negative G accelerationsof the craft to prevent functioning of the by-pass means when slugs ofair arising from positive and negative G accelerations pass through thecooling system.

' 5. In combination with an aircraft engine including an oil circuit toand from the engine, an oil cooling system in the circuit, and by-passmeans in the circuit responsive to the occurrence of aberrations inpressure of the oil flow through the cooling system to shunt the latter,solenoid controlled means operable upon energization of the solenoid toprevent the by-pass means from shunting the cooling system when theaberrations of the oil flow pressure through the cooling system resultfrom positive and negative G accelerations of the aircraft, andelectrical switch means responsive to positive and negative Gaccelerations of the craft to energize the solenoid.

6. In the combination as set forth in claim 5, wherein the Gacceleration responsive switch is associated with timing means forholding the solenoid energized for a predetermined period.

References Cited in the file of this patent UNITED STATES PATENTS1,595,433 Vincent Aug. 10, 1926 2,312,234 Brandt Feb. 23, 1943 2,327,342Drapeau Aug. 24, 1943 2,336,784 Goodman Dec. 14, 1943 2,512,189 WatermanJune 20, 1950 2,573,477 McIntosh Oct. 30, 1951 2,573,479 McNerney Oct.30, 1951 2,641,277 Booth June 9, 1953

